Fearing he has left the door open for Banquo's family to overthrow him, Macbeth enlists two murderers to take out Banquo and Fleance.
Macbeth tells lady Macbeth that he needs to kill Banquo and Fleance because killing Duncan wasn't enough to secure the throne.
The two killers are joined by a third and attempt to kill Banquo and Fleance, though thy can only kill Banquo as Fleance runs off.
Macbeth learns that the murderers have killed banquo but Fleance has escaped, though this upsets Macbeth he is confident still he can keep the throne. At the feast Banquo's ghost is in his seat, Macbeth scares off his guests as he speaks to the ghosts.
Hecate is upset with the three witches for meddling with Macbeth and Banquo without Hecate. She then says she will take over and instructs the witches to give Macbeth a false sense of confidence.
Lennox and a lord walk together discussing what they think of Macbeth. Both call him tyrant and believe he, not Fleance who most blame, had killed Banquo. they also talk about Macduff leaving for England to team up with Malcolm to take down Macbeth.